Noted a couple of fresh slab avalanches out there today. Both were on northerly aspects around 9300'. Photo: B. Fredlund
Noted a couple of fresh slab avalanches out there today. Both were on northerly aspects around 9300'. Photo of one attached.
We skied up the northeast face/gully on Ross Peak, and dug a pit just under the summit of the east face, just before the slope angle increased to reach the summit. This was the last part of the approach to the Banana couloir. We noticed variable snow depths on the way up, and intermittent wind slabs of about 4 inches deep on the way up. Our pit resulted in an ECTP19. The propagation went the full plane of the column, and broke about 8 inches from the ground on a harder layer with sugary snow above and below it. Other than the harder layer, most of the bottom of the snowpack seemed loose and faceted, with about a foot of powder on top. We ended up turning around before entering the steeper angled terrain.
Digging a pit near East Hotel Creek in Island Park where we found a layer of surface hoar buried two feet deep. Photo: GNFAC
Avalanche previously reported on Monday on Henderson (photo taken 1/17). GNFAC
Snowmobiled to lower rock island lake and ascended to 9200ft. Mostly sunny skies with no wind. No avalanches observed, no collapsing, minor cracking right around skis in wind affected areas 4 inches deep. Dug on due N aspect. HS = 120-150 cm. Soft surface 4-6 inches. 1 finger hard layers with rounding facets in between with 2 layers of concern about 1 foot down and 1 foot off the ground where 4F rounded facets are sandwiched between harder layers. CT6 Q2 down 4 inches on old snow surface. CT 23 Q3 on basal facets.
Snowmobiled to lower rock island lake and ascended to 9200ft. Mostly sunny skies with no wind. No avalanches observed, no collapsing, minor cracking right around skis in wind affected areas 4 inches deep. Dug on due N aspect. HS = 120-150 cm. Soft surface 4-6 inches. 1 finger hard layers with rounding facets in between with 2 layers of concern about 1 foot down and 1 foot off the ground where 4F rounded facets are sandwiched between harder layers. CT6 Q2 down 4 inches on old snow surface. CT 23 Q3 on basal facets. ECTN 6 4 inches down, ECTN 29 about 1 foot down (consistent with last weekend observation in this area). Stubborn old snowpack right now with lack of significant new snow or wind and recent warm temps. Still poor structure in areas where snowpack is thinner, however where it is deeper seems facets are healing.
<p>A heightened avalanche danger exists in the mountains near Big Sky through the Lionhead area and Cooke City. In the last four days, 7-10” of snow around West Yellowstone and Cooke City and 5” near Big Sky incrementally loaded a layer of weak surface hoar crystals buried 1-2’ deep. This weekend, we know of two skier-triggered avalanches near Hebgen Lake that failed on this layer (<a href="http://mtavalanche.com/node/27665"><strong><span>observation</span></st…;, <a href="https://www.mtavalanche.com/node/27664"><strong><span>photo and details</span></strong></a>). Yesterday, Alex saw a rider-triggered avalanche on Henderson Mountain that occurred in the last couple of days (<a href="https://www.mtavalanche.com/node/27681"><strong><span>photo and details</span></strong></a>). During field days, we have seen this layer on many slopes from Big Sky through the southern portion of the advisory area (<a href="https://youtu.be/jQg8gqFqn1M"><strong><span>Beehive Basin</span></strong></a>, <a href="https://www.youtube.com/watch?v=hk_6xgHgTCo"><strong><span>Buck Ridge</span></strong></a>, <a href="https://youtu.be/1mFc__nNwIk"><strong><span>Lionhead video</span></strong></a>, <a href="https://www.youtube.com/watch?v=iBS_5itbX_U&list=PLXu5151nmAvTi1DBS… City video</span></strong></a>, <a href="https://www.youtube.com/watch?v=ECi646U0Rtg&list=PLXu5151nmAvTi1DBS… Fork video</span></strong></a>). While its distribution can be spotty, assume it is on all slopes and can produce avalanches if we ride or ski across the wrong spot.</p>
<p>Avalanches within the new and wind-drifted snow like a natural avalanche observed in Cooke City this weekend (<a href="https://www.mtavalanche.com/node/27660"><strong><span>details</span></s…;) and slides breaking on weak layers buried deeper in the snowpack are also possible.</p>
<p>Dig, test and maintain a conservative mindset when selecting terrain due to persistent weak layers demonstrating a potential to fail and avalanche. Dangerous, human-triggered avalanches are possible today, and the danger is rated MODERATE.</p>
<p>In the mountains around Bozeman, 3-6” of snow has fallen since the start of the weekend. Yesterday, skiers near Alex Lowe Peak noted small loose snow avalanches and another near Lick Creek was able to trigger a very small avalanche on a steep rollover in a 4” deep wind drift (<a href="https://www.mtavalanche.com/node/27689"><strong><span>photo and details</span></strong></a>, <a href="https://www.mtavalanche.com/node/27686"><strong><span>observation</span…;). Similar avalanches are possible today and will increase in size and likelihood if the wind picks up. As Alex noted in his <a href="https://youtu.be/UhWH5MvlW84"><strong><span>video</span></strong></a> from Mount Blackmore, without the loading from a more significant snowfall event, avalanches breaking deeper in the snowpack are less likely. However, the structure is poor, with weak layers near the ground and in the middle of the snowpack. Two groups of skiers over the MLK weekend noted this structure in the Bridger Range (<a href="https://www.mtavalanche.com/node/27673"><strong><span>observation</span…; 1</span></u></strong>). One of the two groups chose to retreat to conservative terrain after getting unstable test results in Frazier Basin (<a href="https://www.mtavalanche.com/node/27671"><strong><span>observation</span…; 2</span></u></strong>).</p>
<p>Mitigate the avalanche danger by testing weak layers deeper in the snowpack before considering skiing or riding on steeper slopes and selecting terrain that minimizes the consequences of triggering a slide.</p>
<p>The danger is rated MODERATE.</p>
<p>Please share avalanche, snowpack or weather observations via our<a href="https://www.mtavalanche.com/node/add/snow_obs"><span> </span></a><a href="https://www.mtavalanche.com/node/add/snow_obs"><strong><span>website</s…;, email (<strong>mtavalanche@gmail.com</strong>), phone (406-587-6984), or Instagram (#gnfacobs). <span><span> </span></span></p>
<p>A heightened avalanche danger exists in the mountains in Island Park. In the last four days, 12” of snow total has incrementally loaded a layer of weak surface hoar crystals buried 1-2’ deep. Slides within the new and wind-drifted snow and avalanches breaking on weak layers buried deeper in the snowpack are possible. Dig, test and maintain a conservative mindset when selecting terrain due to persistent weak layers demonstrating a potential to fail and avalanche.</p>
<p>Doug and I will be riding in the Centennial Range today. Follow the GNFAC’s social media channel’s this evening for a video about what we find.</p>
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
TONIGHT, Tuesday, January 17th, 6 p.m., Silent auction and ski movies to support the Darren Johnson Memorial Avalanche Education Memorial Fund @ The Independent in Big Sky, $10
